1. Field of the Invention
The present invention relates to a method for forming a perovskite type oxide thin film having a plurality of A-site elements or B-site elements, piezoelectric element having a piezoelectric substance constituted of a perovskite type oxide thin film formed by the film forming method, liquid discharge head having the piezoelectric element, and liquid discharge apparatus having the liquid discharge head.
2. Description of the Related Art
Recently, researches of a ferroelectric thin film and piezoelectric electrostriction thin film are frequently performed as application to an FeRAM, application to an optical shutter and optical communication, and application to a piezoelectric actuator. In this case, as a material having a large piezoelectric characteristic, a relaxor state of single crystal material is reported. It is said that the relaxor state of single crystal material shows a large piezoelectric characteristic for the azimuth (100) of rhombohedral. The relaxor state of single crystal material is made by a fusion method such as a flux method or bridgman method (Non-patent Document 1). Therefore, it is necessary to cut, work, and join a single crystal material to form it into a device and its size is limited. For example, there are problems that it is impossible to develop a micromachine (MEMS; Micro Electro Mechanical System) to a minute device or it is impossible to obtain a long ink-jet head. Moreover, Ruddelsdon-popper-type oxide and Bi-layer-like compound are noticed as non-lead-based piezoelectric materials including the purpose to an FeRAM.
Furthermore, it is conventionally difficult to form a relaxor state of single crystal known as zinc niobate titanate (may be shown as PZN—PT) in the case of the sputtering method or sol-gel method. The reasons are shown below.
In the case of film formation by pulse-laser vapor deposition method (may be shown as PLD method) or sputtering method, due to absence of ceramics, a target material uses a bulk state of single crystal material which is expensive. Moreover, it is difficult to work a single crystal material because it has an insufficient mechanical strength and its workability is not preferable as a target.
In the case of the sol-gel method or metal organic-compound deposition method (may be shown as MOD method), there are problems that it is difficult that the organic-metal compound of Zn which is a material is melted in a solvent when it is coexistent with other material and it is impossible to form a composition in which the content of Zn element is increased into a film.
[Non-patent Document 1] S. E. Park, [Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals], Journal of Applied Physics (J. Appl. Phys.), 1997, Volume No. 82, No. 4, p. 1804